===== Analog Computation #01 - Chua's Circuit =====
This tutorial is part of the workshop [[https://radical-openness.org/en/programm/2020/chuas-circuit-within-analog-computer-chuas-circuit-within-analog-computer-part-1|Chua’s Circuit within an Analog Computer]] of the AMRO20 festival in Linz, Austria 2020.
It is the first lesson about analog computation. And it is about the implementation of a [[https://en.wikipedia.org/wiki/Chua%27s_circuit|Chua's Circuit]] in the analog computer [[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:analog_computer_main|Confetti]]. With this non linear calculation one will get a chaotic oscillation that sounds amazing and looks awesome on an oscilloscope.\\
The Chua's Circuit was invented 1983 by the engineer and computer scientist [[https://en.wikipedia.org/wiki/Leon_O._Chua|Leon O. Chua]].\\
The circuit basically just needs 5 parts:\\
[[https://en.wikipedia.org/wiki/Chua%27s_circuit#/media/File:Chua's_circuit_with_Chua_diode.svg|{{:analogcomputer:1280px-chua_s_circuit_with_chua_diode.svg.png?400|}}]]
//(graphic by [[https://commons.wikimedia.org/w/index.php?title=User:Chetvorno&action=edit&redlink=1|Chetvorno]], [[https://creativecommons.org/publicdomain/zero/1.0/deed.en|CC0]])//
C1 = 10 nF\\
C2 = 100 nF\\
R = 5 kOhm potentimeter\\
L = 15 mH inductor or a gyrator\\
NR = Chua's Diode\\
If the potentiometer is adjusted on the right position the circuit will oscillate in a chaotic manner.\\
{{:analogcomputation:chua_s_circuit_pure_134355.jpg?600|}}\\
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==== Build ====
One can build a Chua's Circuit with the analog computer [[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:analog_computer_main|Confetti]]. Two modules are needed: the Chua's Diode and a Gyrator. A Gyrator is more handy than an inductor so one can use it instead.\\
=== Chua's Diode ===
[[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:confetti116_chua_diode|{{:analogcomputation:confetti116_chua_s_diode_ii_01.jpg?300|}}]]
[[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:confetti116_chua_diode|Chua's Diode]]\\
There are different ways to implenent a Chu's Diode, an alternative Chua's Diode one finds here:\\
[[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:confetti102_chua_diode#confetti102_chua_diode|Confetti 102 Chua's Diode (with real diodes)]]\\
=== Gyrator ===
[[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:confetti101_gyrator|{{:analogcomputation:confetti101_gyrator_03_15mh.jpg?300|}}]]
[[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:confetti101_gyrator|Confetti 101 Gyrator]]\\
=== Power Supply ===
One needs a power supply, too. To get the positive and the negative 9V to power the Confetti boards the easiest way is to use two 9V batteries.\\
[[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:9v_battery_supply|{{:analogcomputation:confett_9v_power_8583.jpg?300|}}]]
[[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:9v_battery_supply|9V Battery Supply]]
=== ... and some Caps and a Poti ===
To build a Chua's Circuit out of these board one needs additionally a breadboard or a [[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:confetti302_breadboard|Confetti302 Breadboard]], some jumper wires, and these parts:\\
* **Capacitors:**
* 1x 100 nF
* 1x 10 nF
* **Potentiometers:**
* 1x 5 kOhm
=== Audio Out ===
For attaching the circuit to an audio mixer one should use an additional high Ohm resistor. Something like 500 KOhm should do.\\
A much better way would be to use a buffered audio output.\\
[[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:confetti103_buffered_output|{{:analogcomputation:confetti103_buffered_output_10.jpg?300|}}]]
[[https://paperpcb.dernulleffekt.de/doku.php?id=analog_computer:confetti103_buffered_output|Confetti103 Buffered Output]]
=== Setup ===
A final setup could look like that:\\
{{:analogcomputation:chua_s_circuit_setup_01.jpg|}}
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==== Schematic ====
{{:analogcomputation:chua_s_circuit_02.jpg?400|}}\\
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==== Buy the Parts ====
One finds all parts on mouser.de:\\
[[https://www.mouser.de/ProjectManager/ProjectDetail.aspx?AccessID=2db9b9b476]]\\
or as a PDF:\\
{{ :analogcomputation:warenkorb_mouser.de_mai09_0601.pdf |}}\\
Additionally one needs some double sided tape to stick the paper printout on the [[https://en.wikipedia.org/wiki/Veroboard|Veroboaord]] and some copper wire for the PCB bridges and some breadboard jumper wires.
It is also possible to replace the [[http://www.ti.com/lit/ds/slos080n/slos080n.pdf?&ts=1590083569530|TL072]] operational amplifier with an [[http://www.ti.com/lit/ds/symlink/lm358-n.pdf?&ts=1590063244194|LM358]], both work the same.
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==== See and Listen to it ====
One can connect an audio mixer (with a 500 kOhm resister) and oscilloscope probes to three different points. X and Y are at the connection of the capasitor and the poti. The third one (Z) is on the gyrator board.\\
{{:analogcomputation:chua_s_circuit_02_xyz.jpg?400|}}\\
An oscilloscope in X-Y mode should look like that:\\
{{:analogcomputation:chua_s_circuit_oscilloscope_134541.jpg?600|}}
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==== Links ====
[[https://www.chaotic-circuits.com/]]\\
[[http://www.chuacircuits.com/]]\\
[[http://nldlab.gatech.edu/w/index.php?title=Group_3_2012]]\\
[[http://www.instructables.com/id/A-Simple-Chaos-Generator]]\\
[[http://www.scholarpedia.org/article/Chua_circuit]]\\
[[http://crossgroup.caltech.edu/chaos_new/Chua.html]]\\
[[http://jamesnsears.com/archive/ecechua.htm]]\\
[[https://hypertextbook.com/chaos/strange/]]\\
[[https://www.vanderbilt.edu/AnS/psychology/cogsci/chaos/workshop/WorkshopF.html]]\\
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==== Thanks ====
This tutorial has been made possible with [[https://gateway.radical-openness.org/|AMRO20 - Art Meets Radical Openes]], 2020.
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==== License ====
Except where otherwise noted, the tutorial and all boards are made by **Wolfgang Spahn** 2016-20.\\
They are licensed under a [[http://creativecommons.org/licenses/by-nc-sa/4.0/"|Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License]].
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